This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Myopia (nearsightedness) is a visual disorder that affects 25% of Americans, at a cost of $4 billion/year. It has recently been identified as a health disparity because it can disproportionately affect some minority groups. While its etiology remains unknown, studies suggest a role for environmental factors. It is important to determine whether viewing distance is a sufficient stimulus to induce a change in refractive error during postnatal development and the earl juvenile period of development, which corresponds to the human time frame when significant rates of myopia begin to emerge. During the reporting period, monkeys were trained on a two alternative forced choice visual matching to sample task, with stimuli that have become increasingly more complex, projected on monitors at a near viewing distance. Under general anesthesia, monkeys underwent regular measurements of refractive error via cycloplegic retinoscopy, measurements of axial length of the eye via A-scan ultrasound, and other measurements of ocular parameters. Data collection continues to determine these functional relationships and to understand the relationship between visual experience, eye growth, and refractive status, and the mechanisms that guide those relationships.